The nuclei comprising the anterior striatum play a critical role in learning and motivation. Derangements of these nuclei are implicated in a broad range of diseases including depression, drug addiction, and learning disorders. Our hypothesis is that there are two streams of information processing in the anterior striatum, dorsal and ventral, that perform complementary but different roles. Specifically, we hypothesize that the dorsal stream, which includes the caudate (Cd), is involved in the executive aspects of associative learning, whereas the ventral stream, which includes the nucleus accumbens (NAc), is involved in providing motivation for the performance of learned behaviors. Recent studies in our lab have demonstrated that intermittent electrical stimulation of the Cd, can significantly enhance the rate of visual-motor learning in primates. Our group is uniquely able to investigate these structures because we are able to perform physiological recordings and electrical stimulation in both primates and humans. This project will test the overarching hypothesis that is that deep brain stimulation of the Cd and NAc can be used to enhance learning in primates and humans. In the first stage of experiments, we will we use electrical stimulation to modulate the activity of the Cd and NAc during associative learning in primates, in order to optimize the parameters for learning enhancement. In the second stage, we will use the implanted DBS devices to assess the behavioral effects of stimulation on learning and motivation. We predict that stimulation in the NAC combined with stimulation in the Cd will lead to a dramatic increase in learning enhancement in both primates and subsequently in humans. Preliminary data is very promising suggesting that the Cd and NAc play distinct roles consistent with our proposed hypothesis. Elucidating the role of these nuclei in learning and motivation will significantly advance our understanding of the brain;and is vitally important to treating disorders that have an extremely large impact on public health.